When you get a voicemail, you can check your message from the notification on your phone. Swipe down from the top of the screen. Tap Voicemail ….You can call your voicemail service to check your messages. Open your device’s Phone app . At the bottom, tap Dialpad . Touch and hold 1. How do you listen to your voicemail from a different phone? Call your 10-digit wireless number. When you hear your voicemail greeting, press the * key to interrupt it. If you reach the main voicemail system greeting, enter your 10-digit wireless phone number, then interrupt your greeting by pressing the * key. Can I listen to my voicemail without setting it up?
Voicemail can be reached using any voicemail access number from any phone or voip app.Voicemail can be reached by dialing ones own 10 digit phone number from any phone or voip app.Voicemail can be reached by pressing and holding 1 on the phones keypad.

Pro tip: You can double-check to see if voicemail is set up on your iPhone by dialing and calling your own phone number in the Keypad of the Phone app, or by calling your iPhone using another phone.
If you have a visual voicemail applications installed on your Galaxy S21, you can alternately use that app to record and set a greeting instead.